Here are the suggested answers for the exercise, filled in:

**Simple Past & Past Continuous**

1. It **was** (when I **woke up**) this morning.
2. When my dad **came** home, we **were having** dinner.
3. The neighbors **were playing** loud music when I **called** the police.
4. She **hurt** her leg while she **was riding** her bike.
5. While they **were watching** a horror movie, they **heard** a strange noise.
6. He **was** sick while he **was swimming** in the pool.
7. I **was doing** my homework when the lights **went** out.
8. The police **caught** him while he **was stealing** a TV from a store.
9. When I **saw** them, they **were sitting** under a tree in the park.
10. He **lost** his favorite sunglasses while he **was hiking** in the mountains.

**When - While**

1. The students were doing an exercise **when** the bell rang.
2. I saw an accident **when** I was waiting at the bus stop.
3. **While** she was writing an email, her computer turned off.
4. He fell down **when** he was climbing a tree.
5. **While** my mom came home, my sister was sleeping.
6. We found some old photographs **while** we were tidying our room.
7. **When** you called me last night, I was studying for the test.
8. I had a bad dream **while** I was sleeping on the sofa.
9. **When** the fire alarm went off, we were listening to music.
10. She started to cry **when** she was watching a movie.

Feel free to adjust any word choices if needed!